Cystic Fibrosis - Medical Case Study

Cystic Fibrosis

Medical Case Study

Lisa Fagerstedt

12/7/2011

The respiratory system consists of two parts which are the upper and lower respiratory tracts. The upper respiratory tract consists of the nose, mouth, larynx and trachea. The lower respiratory tract consists of the lungs, bronchi and alveoli. The alveoli are tiny air filled sacs at the furthest reaches of the bronchial tree. Gas exchange occurs in the alveoli where carbon dioxide is exchanged for oxygen. Mucus lines the respiratory tract. Its purpose is to keep the air moist and to protect the lungs from airborne pathogens during inhalation. Mucus contains antibodies that trap and kill most infectious agents that enter the lungs through respiration.

Respiration begins upon inspiration when air enters the nose or mouth and travels through the larynx, down the trachea and through the bronchi which are the largest branches of the bronchial tree. There are two bronchi which branch into the right and left lungs. The main bronchi divide even smaller before becoming the bronchioles. At the end of them are the alveoli. These are tiny, balloon like air sacs where gas exchange occurs. The oxygen taken in through inspiration is exchanged for carbon dioxide which is let out through exhalation.

The pancreas and liver support digestion through secreting enzymes into the duodenum. The duodenum is the first part of the small intestine where the stomach releases partially digested food. These organs secrete their enzymes through ducts. The gallbladder stores the digestive enzymes called "bile" and allows a small continual amount to be secreted into the duodenum. Bile contains water, bile salts, bile pigments, cholesterol and electrolytes. Bile salts are the only part of bile with a function in digestion. They help with digestion of fatty acids and some fat soluble vitamins. The enzymes in pancreatic juice contain amylase which breaks down carbohydrates and lipase which breaks down fat. It also contains enzymes that break down proteins which are called proteinases. The pancreas also secretes enzymes that break down nucleic acid into nucleotides.

In the male reproductive system, the vas deferens is the tube which carries the sperm from the testicles to the penis. Sperm are stored in the testes which are located in the scrotal sac (scrotum). Sperm are transferred to the epididymis, which are coiled tubules also in the scrotum, before they move through the vas deferens. During ejaculation the sperm travel through the vas deferens over and around the bladder. They meet with the seminal vesicles at the ejaculatory ducts. The seminal vesicles secrete fluid which mixes with sperm to create semen. The fluid from the seminal vesicles contains mucus, amino acids, fructose and prostaglandins. The ejaculatory ducts empty into the urethra. The prostate gland also secretes fluids into the urethra. These fluids protect the semen against acidity of urine and vaginal fluid. For the purpose of this report, the vas deferens and the explanation of the function are all that are necessary.

Abnormally thick sticky mucus is the main problem with cystic fibrosis sufferers. In healthy individuals thin slippery mucus is found throughout the body where it is secreted by cells lining the mucus membranes. It is also found lining the epithelial cells of many organs. It helps to keep diseases out and keeps the mucus membranes moist. In some organs it transports enzymes to different places in the body. Mucus consists of sodium, chloride and water. It is pushed to the surface of the membranes cells through chloride channels. These channels consist of the calcium-dependent chloride channel, the outwardly rectifying chloride channel (ORCC), and the main channel in the airways is called the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR is the main channel for sodium, chloride and water in the lungs and related airways. Consistency of mucus, that is its thickness and slipperiness, is determined by the amount of chloride and sodium, and also the amount of moisture (water) that is secreted through these channels. Although a healthy person may have times when thick, sticky mucus fills their airways because of a viral or bacterial infection, most of the time the mucus will remain the right consistency to function well.

CFTR is a protein product of the gene called CFTR. According to the U.S. library of medicine it belongs to a family of genes that are called the ATP-binding cassette transporters. These proteins use ATP to transport different molecules across cell membranes. It is responsible for the production of thin, freely flowing mucus in the lungs and respiratory airways as well as the digestive system, reproductive system and other organs and tissues. (US Library of Medicine)

A genetic mutation in the CFTR gene is responsible for the disease of cystic fibrosis. The main complication of the disease is with the lungs, but it affects the pancreas, digestive and reproductive systems (mainly in males) as well. According to the data collected by the Cystic Fibrosis Foundation, "there are about 30,000 Americans, 3,000 Canadians, and 20,000 Europeans with Cystic Fibrosis. The disease occurs mostly in whites whose ancestors came from northern Europe, although it affects all races and ethnic groups. Accordingly, it is less common in African Americans, Native Americans, and Asian Americans. Approximately 2,500 babies are born with CF each year in the United States." (Cystic Fibrosis Foundation)

People who suffer from cystic fibrosis are prone to lung infections caused by bacteria that become trapped in the thick sticky mucus characteristic of this disease. These infections will progressively and irreparably damage the lungs. Mucus will also block the pancreas causing digestive problems which lead to malnutrition. Children with cystic fibrosis typically have poor growth and development, but the outlook for quality of life continues to improve in recent years due to research, early diagnosis, and treatment developments.

According to the Human Genome Project Information Website, "CF is an autosomal recessive disorder caused by mutations in the CFTR (cystic fibrosis transmembrane conductance regulator) gene. Heterozygous carriers (those who have inherited only one copy of the altered gene) are asymptomatic. Two altered genes must be present for CF to appear. This means that if both parents are CF carriers, their offspring would only express CF symptoms if they had inherited one defective copy of the CFTR gene from each parent." (National Human Genome Research Institute) We all have two copies of the CFTR gene and in